There are numerous designs for sign systems in which the messages imparted by the overall sign can be changed. The location of the sign system may have an impact on the ease with which these messages may be changed. One convenient approach is a sign system with changeable panels. On the one hand, there is a desire to facilitate changes and minimize the time and effort involved. But if the sign system is located where it is not under continual surveillance by authorized person while it is exposed to the general public, there is a concern with inhibiting unauthorized changes. These opposing goals are readily evident in the case of directional signs in buildings with multiple facilities, such as an office building with multiple tenants. The signs are often located where they are only observed by the general public during the time that the building is open but frequently require alteration as tenants change. It is advantageous if the changes can be made without the need to have a key or other unique opening device.